OK i've found a solution that works for me!
SHORT ANSWER:
- go to the library icon in the navigation pane of windows explorer and right-click, then select "restore default libraries".
This allowed me to not only view photos in 'photos app', but it also allowed me to browse for a lock screen and account picture. i knew they were linked issues, ha!!
LONG ANSWER:
Restore default library is what i expect made the difference on my system, but I did try a host of other things and just in case any of these were necessary for the process, i'll detail what i did here:
(a) i enabled permissions as suggested here:
When i go into the photo app it says can't find picures - Microsoft Community. Though my SYSTEM and Administration permissions were as recommended in the post, I also enabled full permissions in the 'Users' group.
(b) i enabled indexing as suggested in another post on microsoft forums (sorry, i didn't get the url) but the process goes: open charm (win + c), select 'search' (the magnifying loop), select 'settings' and type the keyword 'index'. "indexing options" ought to come up as the first result. click on it, then add the C: drive (mine was not there), by selecting "modify", if i remember correctly. This takes a while to process.
(c) rebooted once (b) was complete, but there was not change in photos app or image browsing in customisation settings.
(d) created new user
- a microsoft MVP suggested, in answers.microsoft.com, to create a new user and see if that user has a working photos app. Copied all photos to the pictures directory. Went to photos app and 'add photos here' - screen said 'updating…. This can take a while if you have many photos". left on while I went to work (I have just under 10,000 photos, so didn't think this was so unreasonable). 11 hours later screen and message had not changed.
- checked windows explorer and libraries icon there, but no actual 'libraries'. Tried to right-click 'create new library', but got an error. Right-clicked again and checked out what else there was to choose from in the context menu and saw 'restore default libraries' - clicked that and libraries appeared showing the pictures folder.
- Back to photos app - YAY! Displaying all photos (haven't checked, but there are a lot). only a couple of minutes to bring up all photos.
(e) switched back to my account. restored default libraries and this triggered photos app to show photos. yay!
so the next and last step is to remove the duplicated photos from the test user account and remove that account, but i'm ecstatic that i finally figured this out for myself, even if it did take 5 solid hours of troubleshooting! hopefully this post will help others avoid the same frustrations!
Agnieszka.